在Flask下使用boto的Dynamo Db JSONResponseError

Question

我有这个模块连接到Dynamo，创建一个会话表，并在其中放置一个项目：

import boto.dynamodb2
from boto.dynamodb2.table import Table
from boto.dynamodb2.fields import HashKey
from boto.regioninfo import RegionInfo
from boto.dynamodb2.layer1 import DynamoDBConnection
import uuid

try:
    sessions = Table(
        table_name='IssueBoxSessions', 
        schema=[HashKey('SessionId')],
        connection=DynamoDBConnection(
        region=RegionInfo(name='eu-west-1',
                          endpoint='dynamodb.eu-west-1.amazonaws.com')
        ))
except:
    print("Dynamo can't connect")

def create_session():
    id = str(uuid.uuid4())
    res = sessions.put_item(data={
        'SessionId': id,
        'data': {
            'user_id': 1, 
            'ip': '10.1.1.10',
            'datetime': 'now'
        }
    })
    print(res)
    return res

请注意，我正在开发和测试EC2实例，并使用附加到实例的IAM角色对Dynamo进行身份验证。

因为我正在使用IAM，所以身份验证不需要代码。它们允许实体（我的实例）访问某些服务（dynamo）。它们旨在防止必须将访问密钥放入某些AWS资源的代码中。如果是认证的情况，它也不适用于解释器。我相信这个问题来自IAM身份验证之外的其他问题。

所以当我在python解释器中导入这个create_session函数并调用它时，它可以工作：

>>> from issuesite.session_handler import create_session
>>> create_session()
True
True

但是，当我尝试在烧瓶附近的任何地方使用它时，它会熔化：

from flask import request
from issuesite.session_handler import create_session
from issuesite import app

@app.route('/login', methods=['GET'])
def login():
    if create_session():
        return "ok"

抛出的错误是：

JSONResponseError: JSONResponseError: 400 Bad Request
{u'message': u'The security token included in the request is invalid.', u'__type': u'com.amazon.coral.service#UnrecognizedClientException'}

事实上，这是所有美丽的全部追溯：

Traceback (most recent call last):
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
  return self.wsgi_app(environ, start_response)
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
  response = self.make_response(self.handle_exception(e))
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
  reraise(exc_type, exc_value, tb)
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
  response = self.full_dispatch_request()
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
  rv = self.handle_user_exception(e)
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
  reraise(exc_type, exc_value, tb)
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
  rv = self.dispatch_request()
File "/server/flask/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
  return self.view_functions[rule.endpoint](**req.view_args)
File "/server/issuesite/views/base.py", line 14, in login
  if create_session():
File "/server/issuesite/session_handler/__init__.py", line 29, in create_session
  'datetime': 'now'
File "/server/flask/lib/python2.7/site-packages/boto/dynamodb2/table.py", line 821, in put_item
  return item.save(overwrite=overwrite)
File "/server/flask/lib/python2.7/site-packages/boto/dynamodb2/items.py", line 455, in save
  returned = self.table._put_item(final_data, expects=expects)
File "/server/flask/lib/python2.7/site-packages/boto/dynamodb2/table.py", line 835, in _put_item
  self.connection.put_item(self.table_name, item_data, **kwargs)
File "/server/flask/lib/python2.7/site-packages/boto/dynamodb2/layer1.py", line 1510, in put_item
  body=json.dumps(params))
File "/server/flask/lib/python2.7/site-packages/boto/dynamodb2/layer1.py", line 2842, in make_request
  retry_handler=self._retry_handler)
File "/server/flask/lib/python2.7/site-packages/boto/connection.py", line 954, in _mexe
  status = retry_handler(response, i, next_sleep)
File "/server/flask/lib/python2.7/site-packages/boto/dynamodb2/layer1.py", line 2885, in _retry_handler
data)

Answer 1

从您发布的代码中，您使用的是Boto的常规连接方法，而您应该使用特定于IAM（http://boto.readthedocs.org/en/latest/ref/iam.html）的代码。

我希望这有帮助。

Answer 2

这看起来像凭证问题。您使用的是正确的凭据吗？看起来类似于这个issue。可能值得设置debug logger以查看从哪里/哪些凭据被拉出。

Answer 3

我尝试使用实际的AWS凭据而不是IAM角色，最后我采用了实例的AMI并使用相同的IAM角色从其中启动了另一个实例，有趣的是，与Dynamo交谈时没有任何问题。

我最后继续更换实例。

但是，我无法确定究竟是什么导致了这个问题。